(Parts of this background may or may not constitute prior art.) Fiber-to-the-premises (FTTP) from local telephone and cable service providers is rapidly being implemented. This service requires a broadband optical fiber distribution network comprising local optical fiber distribution cables that are installed in neighborhoods and city streets. The local distribution cable is a large fiber count (multi-fiber) cable. Single fiber or few fiber cables are used for the “drop” line from the street to the premises. In many cases, aerial drop lines are used, and these have special requirements. In other cases, buried drop lines are used, and these have different requirements.
Optical fiber drop cables are made in several designs. Most of these designs mimic earlier copper cable versions. In many cases, physical resemblance is deliberate, so that the external cable appearance matches that of existing copper versions, and standard hardware and installation equipment may be used for both. Thus “A-drop” optical fiber cable is an optical fiber version of A-drop copper cable, and is made in the same flat or ribbon-like configuration. Aerial drop cable typically has one or more strength members for support. A common A-drop or flat cable design comprises one or more optical fibers between two strength members. See for example, U.S. Pat. Nos. 4,761,053, 6,836,603, and 6,501,888.
Optical fiber cables also commonly contain gel-filling compounds for preventing water excursion in the cable. When water enters a filled cable, flow of water along the length of the cable is blocked by the gel. However, gel filled cables are time consuming to install and repair, as the gel must be completely removed from the optical fiber prior to fusion splicing operations. Moreover, since the drop wire is typically attached to the side of a customer's home or building, bleeding of ingredients in the cable onto the customer's building may cause cosmetic or other problems. Optical drop cables containing gel compounds may also be factory preterminated or ‘connectorized’ using ‘plug and play’ optical connectors. In this case the time and expense of field fusion splicing may be avoided through factory installation of an outside plant rated connector. However, factory assembly personnel pre-installing the connectors face issues with time-consuming, expensive complete removal of gel prior to connectorization.
Since aerial drop cables are subjected to considerable stress and sag due to wind and ice build-up, these cables typically have reinforcement members both to support the cable and to protect the optical fiber module inside the cable. A common arrangement is to center the optical fiber(s) between two strength members. The optical fibers are contained within an optical fiber module, bounded on each side by a round strength member. The centers of the optical fiber module and the strength members are typically arranged in-line. The resulting cable cross-section is typically has a flattened, elongated, race-track shape.
Experience with installation and use of these cables has revealed several disadvantages to the basic cable design.                1. Stiffness. These cables are rigid and stiff and difficult to bend or handle.        2. Size. The 300 lb. tensile requirement (Telcordia GR-20 and ICEA-S-717 standards for Outside Plant optical cables) leads to a large cable footprint, typically about 4×8 mm, often used to house a single optical fiber 0.25 mm in diameter.        3. Non-circular cross-section. More difficult to manufacture and handle        4. Not flame retardant. Typically terminated outside the home and the signal must be transitioned to the indoor network. Part of this is a function of size.        
New designs for FTTP drop cable that offer compact size and low cost are continually being sought. In many applications it is desirable to use an optical drop cable indoors, for example to transition from the outdoor network to an indoor ‘set-top box’ optical network unit that will receive the optical signal and decode voice, data, and video signals. Alternately optical drop cables may be used indoors to provide service to multi-dwelling units (MDUs) such as condominiums, townhouses, or multi-story apartment buildings. One approach to design of optical cables for this environment is to: omit large fiberglass strength members used in outdoor cables, use instead aramid strength yarns; reduce the tensile load rating of the cable; and jacket the cable with a flame-retardant plastic compound, suitable for indoor use. This results in a compact indoor cable, and is typically the option chosen for current installations. For example, 3.0 mm diameter indoor interconnect cordage with a tensile rating of 50 to 100 lbs. is often used for this application. However, there are several drawbacks to this also; the indoor cables are less robust than outdoor cables, and the service provider must arrange for a transition from the outdoor network to the indoor network for this application.
Therefore, it would be desirable to have a single compact cable design that is suitable for the drop (outside) portion of the installation, and also for the indoor wiring, such that it may be passed between the two environments with no transition required.
In summary, existing drop cable designs are large and stiff, and not suitable for use in both outside and inside installations. Typical cable designs for inside wiring are not adequate for outside service.
A single cable design that meets the criteria for both inside and outside FTTH installations would represent a significant advance in the art.